Field of the Invention
In some embodiments, the present invention generally relates to beam-shaping optics for lighting devices, lighting device attachments for mobile devices, portable illumination devices for performing videography and photography with mobile phones and other mobile devices, and the use of such portable illumination devices as flashlights and as sources of electrical power for the recharging of batteries in mobile devices.
Related Art
Lighting devices, such as flashlights, headlamps, and others, typically include reflective optics for projecting light from a light source from the lighting device. Conventional reflective optics for projecting light onto distant objects are typically paraboloidal in shape. Paraboloidal reflective optics produce a narrow collimated beam centered on a wide-angle surround beam of much lower intensity. The peak intensity produced by such optics can approach the maximum peak intensity value theoretically achievable using a given light source, for a specified exit-pupil area. However, the surround-beam intensity outside the central collimated portion of beams produced by paraboloidal reflective optics is typically lower than would be preferred by most users, even for viewing objects at relatively short ranges.
In addition, the beam quality (i.e., beam smoothness) produced by a paraboloidal reflector is often poor in the central collimated region due to imaging of various structures in the light source. For this reason, the paraboloidal shape of the reflector is often modified slightly by the addition of texturing on the surface of the reflector. This texturing has the effect of diffusing the collimated portion of the output, thereby producing a smoother collimated output. The texturing is often created by spraying droplets of a viscous liquid onto the reflector's surface and allowing it to solidify. The effect of such texturing on the optical output is difficult to control, so considerable trial and error in spraying the droplets is often required to achieve satisfactory results. An alternative to such texturing is to place a refractive diffuser behind a protective cover glass of the flashlight. However, this increases the cost of the flashlight and reduces the light output due to Fresnel reflection.
Paraboloidal reflectors also generate a surround beam that commonly extends out to off-axis angles beyond which the light is of benefit to the typical user. It would be preferable in most cases to transfer some or all of this light to angular regions closer to the optical axis. This can sometimes be achieved by reducing the focal length of the paraboloid, thereby producing a deeper reflector that collects and collimates more of the light from the source and reduces the angular width of the surround beam. However, in many cases reducing the focal length can be difficult or impossible due to the need to avoid a reflective surface that is impractically close to the light source and prevents providing sufficient space for the light source to be mounted with adequate clearance. It would therefore be desirable to provide improved reflectors for lighting devices.
Mobile devices such as cameras, smartphones, tablets, personal digital assistants, laptop computers and others often include one or more light sources such as light emitting diode light (LED) light sources. These light sources are sometimes operated in conjunction with an image sensor in the mobile device to capture still or video images by using the light sources to illuminate the imaged scene. In other applications, the light sources are sometimes used as a temporary substitute for a flashlight.
The ever-present consumer demand for lighter and smaller devices and for longer battery life in the devices poses a challenge to provide light sources in mobile devices that provide sufficient illumination, illumination of a desirable color, and/or illumination with an effective beam shape for image capture and other scene illumination purposes without creating undesirably bulky or power hungry devices. It would therefore be desirable to provide improved lighting capabilities for mobile devices.
Mobile devices such as cameras, smartphones, tablet computers, personal digital assistants, laptop computers, and other similar devices generally include one or more built-in illuminators that utilize light sources such as light emitting diodes (LEDs). These built-in illuminators are operated in conjunction with a camera in the mobile device to supplement ambient illumination when capturing still and/or video imagery at short ranges (e.g., several feet). Such illuminators are sometimes also used as backup flashlights.
The built-in illuminators in current mobile devices generally provide inadequate illumination under low-ambient-lighting conditions for still photography and, especially, for videography at substantially longer image-capture ranges (e.g., up to 50 feet). Even for scenes illuminated by moderate to high levels of ambient light, these built-in illuminators often fail to provide adequate supplemental illumination to reduce image contrast to acceptable levels when there are large differences in the level of ambient illumination between different regions within a scene to be imaged (e.g., a person standing in a shaded area with a light-colored, sun-illuminated building in the background). Therefore, there is a need for improved illuminators capable of producing significantly higher intensity levels for use with mobile devices.
Due to constraints on weight, volume, shape (e.g., thickness), and available electrical power, it is difficult to incorporate into a given mobile device a built-in illuminator that provides adequate performance over a wide range of commonly encountered ambient lighting conditions, particularly in the case of small mobile devices such as mobile phones, and also particularly for videography. Therefore, a stand-alone portable illumination device that can be utilized as needed with one or more mobile devices can provide significant performance benefits relative to built-in illumination devices.
There is demand among some consumers for the ability to reduce or eliminate unnatural color casts in images captured by cameras in mobile devices via adjustment of the color temperature of the light produced by the illuminator The built-in illuminators in most current mobile devices have no capability for adjustment of the color temperature. Although color casts can be adjusted in post processing of images (e.g., using Photoshop or similar software), it would be far preferable, particularly in the case of video imagery, to use an illuminator with an adjustable color temperature.
The output angular beam widths and beam shapes provided by built-in illuminators in the vast majority of current mobile devices are rotationally symmetrical and non-adjustable, even though the horizontal and vertical field of view (FOV) of still and video imagery captured by a given mobile device can vary greatly depending on its settings (e.g., zoom setting or video-format setting). The light projected by an illuminator outside the camera's FOV does not contribute to illuminating the scene being captured and represents a waste of energy. It may therefore be desirable to provide illuminators with adjustable beam widths and beams shapes for use with mobile devices.